In general, a user uses an input key to manipulate a mobile terminal apparatus such as a mobile phone, a personal handy phone system (PHS) terminal, a personal digital assistant (PDA), and a digital audio player (DAP). For example, usage of a mobile phone provided with a key backlight, which shines key input unit, is becoming more common considering manipulation carried out in the darkness.
Providing the key backlight for manipulation using the input key is especially important for the mobile terminal apparatus having down sized keys.
As a relating technique, PL 1 discloses a technique that causes an operation key unit to function as unconventional notifying means by making the operation key unit in a main body to emit or blink light in various manners or various colors according to phone operations of the mobile phone.
PL 2 discloses a technique that causes keys in an operation unit to emit different colors of light to improve efficiency for key discrimination and key manipulation based on the emission colors at the time of the key backlight emission.
As above, regarding the key backlight which emits the light on the key input unit of the mobile phone terminal, the usage of the techniques causing the key backlight to emit light can help key input by the user and enhance the usability.
{Citation List}
{Patent Literature}
    {PL 1} JP-A-2001-217904    {PL 2} JP-A-2005-134998